The present invention concerns a metering method and apparatus for supplying a commercial washing apparatus or laundry with water-soluble or water insoluble powdered or granulated detergent concentrate from a delivery container to the storage bin of the metering apparatus where portions of the detergent are dissolved in or mixed with water and then conveyed to the commercial washing machine or laundry.
The terms "washing machine" and "detergent" are understood to be used here in a general sense and are understood to comprise rinsing and cleaning machines and rinsing and cleaning agents respectively.
The metering methods presently employed in supplying detergents has an operator fill the storage bin of the metering device by hand from the delivery container. The metering devices are electrically or pneumatically driven and operate with water as a conveying and/or solvent medium for the detergent. In some methods the detergent is metered to the wash water by hand, simply so much per given time. Another metering device uses the conductivity of the wash water and detergent added when change beyond a predetermined point occurs. The powdered or granulated material is constantly fed into a hopper where it is mixed with water and flows from the latter by gravity feed into the laundry wash water (see German Pat. No. 1,542,298). There are also devices where the replenishment of detergent is simply a function of time. A given weight of detergent is mixed with water and added to the wash water by pumping it to the washing machine. Finally metering devices are presently used which flush detergent from the storage bin with water and the resultant mixture conveyed to the washing machine by means of a pump or by gravity feed.
A disadvantage of the known detergent metering methods and apparatus is in most cases the formation of dust during the filling of the storage bin on the metering device. Furthermore, the hygroscopic detergent is exposed during the open transportation to the high humidity of the surrounding air, which can lead to lumping and caking. The lifting and transportation of relatively heavy delivery containers (e.g., paper bags of about 55 lbs.) used in the operation of commercial washing machines represents a considerable burden for the operators, particularly in the case of large consumers with a daily requirement of several hundred lbs. of detergent. In the presently used devices with time-dependent metering, where there is no indication of the concentration used, the amount of detergent required, which may be higher or lower depending on the degree of soiling, is not taken into account. The flushing of the detergent from the storage bins with water leads frequently to lumping and encrustation, which can make more difficult or prevent the conveyance of the mixture.